摘要
南海新生代经历过大陆张裂与分离、海底扩张和地块碰撞等构造演化历史,南海北部为被动大陆边缘,南部是碰撞挤压边缘,东部为俯冲聚敛边缘,西部是走滑边缘。在这种构造体制下,形成了许多沉积盆地。北部和西部边缘上发育着张性沉积盆地和走滑拉张盆地;在南部边缘上,其北部发育着张性盆地,南部为挤压环境下形成的盆地,如前陆盆地、前弧盆地;东部边缘上发育着前弧盆地。目前油气勘探实践证明,南海南部的油气资源比北部丰富。究其原因,南海北部为被动大陆边缘,张性沉积盆地的烃源岩体积较小,而南部挤压环境下形成的沉积盆地的烃源岩体积大;北部的地热流较南部小,因此地温梯度也较小,故南部边缘烃源岩的成熟度比北部高;由于南部边缘处于挤压构造环境,在沉积盆地中形成了许多挤压构造,而北部边缘一直处于张性构造环境,形成的构造较少且较小;同时,南部边缘沉积盆地中,烃源岩生烃与构造形成在时间上搭配较好。因此,在南海南部边缘沉积盆地中形成了许多大型油气田,而南海北部边缘沉积盆地中,大型油气田较少,中小型油气田较多。
The South China Sea has undergone a tectonic history of faulting and breaking-up of continental lithosphere, seafloor spreading and collision between the blocks. The north margin was passive,the south was a colliding and extruding margin, the east a subducting margin,and the west a strike-slip one in Cenozoic.Many sedimentary basins were formed in this tectonic system.There are many rifting basins in the north margin; some rifting basins were formed in the north part of the south margin, and a lot of extruding basins were formed in the south part of the south margin, such as foreland and fore-arc basins; some fore-arc basins were formed in the east margin; and some strike-slip basins were formed in the west margin.The south margin has better petroleum potential than the north according to the practice of petroleum exploration. Why there is such a pattern? We believe that the sorth margin was extruding in Cenozoic, and the hydrocarbon-bearing volume was bigger than the north passive margin. Secondly,in the south margin,heat flow and geothermal gradient are higher than in the north, therefore,the maturity of the hydrocarbon-bearing formation is accordingly higher. Thirdly, many oil-bearing structures were formed due to the extruding forces in the south margin in Cenozoic,while structures are very few in the north margin as it is passive. Fourthly, the coordination between the formation time of the structures and the bearing time of hydrocarbon is better in the south margin than in the north. Therefore,a lot of big oil and gas fields exist in the south margin, and few big oil and gas fields were formed and only medium-small oil and gas fields exist in the north margin. So we believe that the south margin of the South China Sea owns richer petroleum potential than the north margin.
出处
《海洋地质与第四纪地质》
CAS
CSCD
北大核心
2005年第2期91-100,共10页
Marine Geology & Quaternary Geology
基金
国家重点基础研究发展规划项目(G20000046705)
